Decolorizing process and composition used therein



.. an. .w

. such process.

NEIL S. KOCHER, OF ROCHESTER, NEW

colored or dyed layer.

atented Feb. 10, 1925.

.7 S F l YORK, ASSIG -NOR TO EASTMAN,KO'DAK COM- PANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

DECOLORIZING PROCESS AND No Drawing.

To all whom it may concern:

Be it known that I, NEIL S. Koomm, a citizen of the United States of America, residing at Rochester, in the county of Monroe andState of New York, have invented certain new and useful Improvements in Decolorizing Processes and Compositions Used Therein, of whichthe following is a full, clear, and exact specification.

This invention relates to a process for removing dye from tinted or colored material and to a composition used therein. One object of the invention is to provide a process for removing dye from such material, like oellulosic films, inexpensively and dependably and under proper control. Another object is to provide a process for removing said dye rapidly, without dissolving' the material, or films. Another object is toprovide an inexpensive composition for use in Other objects will hereinafter appear.

As my invention is especially applicable to the removal of dye from tinted oellulosic bases or supports for photographic film, one embodiment of it will be described in connection with such film by way of example; but the invention is, of course, not limited to this particular illustrative field. Photographic films have come into extensive use, the bases or supports of which contain a The latter is usually, but not necessarily, on the rear side of the support; that is, the side which will be opposite to the light sensitive emulsion or image layer. Sometimes the dye is located throughout the entire oellulosic support.

When scrap or other waste pieces of such colored film base are to be reclaimed or utilized, it is desirable to remove the color; entirely from them, but without dissolving them. At other times it is desirable, if the colored film base is simply too deep in tint but otherwise usable, to lessen the color without dissolving or in any way impairing the film base or support, this reduction being. necessarily under control so as to be stopped when the right degree is reached.

In each of these decolorizing operations the dye is extracted by a suitable liquid. Consequently the rapid removal of the dye from this liquid becomes highly desirable.

Application filed March 7,

COMPOSITION USED THEREIN.

1923. Serial N'm 623,338.

If the liquid should become loaded with the dye, the rate at which it would extract dye from the colored material would be slowed down; and it might become so concentrated that it would even color films instead of decolorizing them. Moveover, a liquid in which a dye of one color has become too concentrated can not be satisfactorily used to lessen the tint of film of a different color. It is, therefore, highly desirable that the dye be rapidly removed or rendered inactive in the extracting liquid, so that practically an uncolored liquid is available for action on film base of any color.-

I have discovered that this result can be attained by treating the dye-extracting liquid withdecolorizing material, such as decolorizing carbon, say bone-char. While the treatment of the liquid with decolorizing material may take place separately from the removal of the dye from the film, it is, in the preferredembodiment of my invention, car ried out practically simultaneously. The dye is removed, for all practical purposes, when it is taken up by or rendered inactive bjy the decolorizing material, such as bone- 0 ar.

In the preferred embodiment of my invention I immerse material to be decolorized in a bath comprising a mixture of dyeremoving liquid and decolorizing carbon.- For a dye-removing liquid I prefer one which has a solvent action with respect to the dye and a temporary softening action on the film without substantially dissolving the latter. This softening'efi'ect is desirable to permit the dye, and its solvent to come into contact with each other. For example, I mix a liquid which is itself a solvent of the oellulosic film and a substance which is a non-solvent of the film, at least one of the substances having a solvent action on the dye. But the proportion'of film solvent in the mixture is kept so small that the bath does not dissolve the film within the time .used for removing the dye; in other words, the non-solvent transforms the solvent tendency of the other ingredient into a slight softening efl'ect.

By way of illustration, I mix 30 parts of acetone with- 70 parts of water and stir therein 8 to 14 parts of bone-char. The

bath need be kept only at ordinary room temperature, although limited warming is permissible to shorten the tune of treatment.

Ordinarily, however, the action is sufliciently rapid without any heating. The film, say standard nitrocellulose tinted base, is immersed in this bath. In order 'to make the action rapid and uniform, it is pref able to agitate the material in the bath or flow the bath in a general direction contrary to the movement of the film. The latter, if desired, may be chopped into small pieces. These, while in loose contact, are stirred or agitated in the liquid, in large scale work being mechanically .moved countercurrent to the bath. If the scrap or cellulosic material were dissolved, a mixed aggregate would be obtained containing dye and bone-char; but by treating the dyed material with my process the color is thoroughly and rapidly leached out, the dye being rapidly adsorbed, because a constantly fresh uncolored liquid. is always available for extraction. Where the dye is not to be removed entirely but a tint or layer is to be subdued in color, it may be run through the above described bath for the right length of time to obtain the desired tint. It is preferable to move the film through the bath without anyportions of it touching each other; that is, if any convolutions are used, the loops should not touch each other. Here again the liquid should preferably move in a direction contrary to the movement of the film. The action is accurately controlled by regulating the time that the film contacts with a bath of given temperature and strength, yet the removal is sufliciently uniform and rapid to meet manufacturing requirements without causing buckling, puckering or other harmful after effects upon the material. As any of the well known devices for fluid treating such materials may. be employed, a description of the apparatus is omitted.

Of course, there are many equivalent baths. For example a 15% solution of methyl alcohol in water or butyl alcohol may be employed. Furthermore the nature of the dye is relatively unimportant, so

' far as my investigations have shown. Many kinds of basic and acid dyes have been removed from dyed cellulosic materials sucvcesslully. While the process is particularly adaptable to the commercial colored nitrocellulose films, which have such extensiveuse at the present time, it can .be used on other cellulosic materials, such as cellulose acetate and cellulose ether supports. The. action of my bath bears out the theory that the decolorizing action of bone-char is purely one of specific attraction for the color substance by the carboniferous ma terial. I do not care, however, to be re-' stricted to this theory except as indicated in the appended claims.

Having thus described my invention, what ing'said liquid with decolorizing carbon.

3. In the process of removing color from 'dyed cellulosic addition compounds, treating said compounds with a liquid which has a solvent action on the dye and a softening action on said compounds, and treating said liquid with decolorizing material.

4. In the process of decolorizing dyed cellulosic film, treating said film with a liquid containing a substance which is a solrent of said film and a substance which is a. non-solvent of said film, at least one of saidsubstances being asolvent of the dye, the proportion of film solvent being sulficientto permit penetration of said dye solvent without substantially dissolving said fihn and treating said liquid with decolorizing carbon. I

' 5. In the process of decolorizing dyed nitrocellulose film, treating said film with a mixture of water and acetone insufficient to dissolve said film, and treating thev mixture with decolorizing bone-char.

6. The process of removing color from dyed cellulosic material, which comprises treating said material with a mixture of dye-removing liquid and decolorizing material.

7 The process of removing color from dyed cellulosic material, which comprises treating said material with a-dye-removing liquid having decolorizing carbon mixed therein.

8. The process of removing color from dyed cellulosic addition compounds, which comprises treating said compounds with a mixture containing a liquid which has a solvent action on the dye and a softening action on said material, and decolorizing material.

9. The process of removing color from dyed cellulosic film, which comprises treating said film with a mixture containing being sufficient for penetration of said'dye sqgent without substantially dissolving the fi 10. The process of removing color from dyed nitrocellulose film, which comprises leaching said film with a bath of acetone,

water and decolorizing bone-char, the proportion of acetone being insuflicient to substantially dissolve said film.

11. A composition for removing color from dyed cellulosic material comprising a flowable mixture of decolorizing material and dye-removing liquid.

12. A composition for removing color from dyed cellulosic material comprising a fiowable mixture of decolorizing carbon and a dye-removing liquid.

13. A composition for removing color from dyed material comprising deeolorizing carbon mixed with a liquid containing a solvent and a non-solvent of said material, the proportion of said solvent being insuiiicient to substantially dissolve said material, at least one of said solvent and non-solvent being a dye solvent.

14. A composition for removing color from dyed nitrocellulose comprising a mixture of water, acetone, and deeolorizing bone-char, the percentage of acetone being insuflicient to substantially dissolve said nitrocellulose.

Signed at Rochester, New York, this 28 day of February, 1923.

' NEIL S. KOCHER. 

